This invention relates to improvements in high vacuum, thin-film deposition systems, e.g. sputtering systems. More particularly, it addresses the technical problem of accurately controlling the temperature of a moving substrate holder which tends to overheat during the deposition process.
In high vacuum systems for depositing thin films of certain materials (e.g. metals, dielectrics, semiconductor, etc.) on substrates, there is a need to reliably and accurately control the temperature of the fixtures used to support the substrates during the deposition process. Typically, such fixtures must withstand the intense heat associated, for example, with the ion bombardment which characterizes the sputtering process, and some means must be provided for dissipating the thermal energy impacted to avoid damage to the substrate and its holder. In most deposition systems, the temperature control problem is complicated by the fact that the substrate receiving the thin-film must be continuously moved to achieve a film of uniform thickness and, perhaps, stoichiometry. Movement of the substrate is most often achieved by mounting the substrate on a rotatably-driven plate or turntable, and temperature control is achieved by circulating a liquid coolant (e.g. water or ethylene glycol). The liquid coolant enters and exits the substrate holder through the rotatably driven shaft which supports such holder. Elastomeric seals are used to contain the coolant where it enters and exits the shaft (external to the vacuum). Typically, these seals are prone to failure through wear and/or corrosion and have a limited useful life. Hence, it would be desirable to provide a mechanism for cooling a moving substrate holder in a thin-film deposition system which does not require the introduction of a liquid coolant through a rotatably driven drive shaft.